lozga July 4, 2016 at 05:19

The winged Juno will go blind at Jupiter

For many years, Jupiter feasted with his beloved in the cold chambers of the outer solar system. Io, Europe and Callisto shared a table with Jupiter, and Ganymede poured wine. But people known for their curiosity, the power of Prometheus fire sent a machine gun to spy on the feast. Those who did not pay due respect to the gods even dared to call the machine gun Juno, in honor of the wife of Jupiter, whom he did not invite to the feast. Then Jupiter was enraged, and, shining with an unbearably bright aurora, blinded Juno.

Old secrets

According to modern cosmological ideas, of all the planets of the solar system, Jupiter was formed first.

It could look like this

Protoplanetary disk and the Sun should have a similar composition, because they were formed from a substance located in one place. Therefore, Jupiter would have to be very much like the sun. However, the Galileo probe, which descended into the atmosphere of the gas giant in 1995, found that the scientists ’calculations were incorrect. Helium on Jupiter was much less than on the Sun, and less than it should have been calculated. Water vapor, carbon, neon, sulfur also turned out to be less than expected. But nitrogen in the form of ammonia was found to be more than calculated. Consequently, our models of the formation of Jupiter and the models of the formation of the solar system are somewhat erroneous.

After the formation, the planet made a rather big journey, moving in orbit and “eating” a mass that could go to something more useful for the future of humanity (like a large and heavy Mars with a full atmosphere).

But the absorbed mass could not form the core of the planet - the substance fell into the dense atmosphere at cosmic speeds and had to evaporate from heating. If Jupiter has a core (and modern science is inclined to this), then a very large planetary germ from heavy elements should have formed in the young Solar system, which contradicts modern models with planetesimals of kilometer size and planetary nuclei with a mass from the lunar to terrestrial.

Finally, most likely, under the influence of Saturn, both planets retreated to the outer solar system, and now Jupiter is turning at a distance of five astronomical units from the Sun. As a result of mysterious processes in the young Solar System, Jupiter has the largest possible physical diameter (a heavier planet will have a smaller diameter due to a larger compression of matter), weighing three hundred terrestrial ones, with its own mini-solar system from many satellites and even small rings. Jupiter can be called a "planet on steroids" - because of the huge mass inside the planet, a cyclopean scale of force acts, and all the phenomena associated with it suffer from gigantism. Jupiter has a colossal size and power in the magnetosphere (14 times stronger than the Earth's), generating giant auroras.

The Juno probe, which is supposed to enter orbit around Jupiter in the evening of July 4, US time, will be immersed in these secrets of the gas giant (the morning will be July 5 in Russia). The tasks that Juno will solve are easy to remember by the abbreviation PSAM - Origin, Structure, Atmosphere, Magnetosphere.

Science Carousel

Jupiter Juno's PSAM will be studied with a diverse set of tools: A
microwave radiometer (MWR) will look 550 kilometers below the edge of the clouds and will be able to determine the water vapor content in the atmosphere. Structurally, it consists of six antennas on the sides of the apparatus: The

Gravity Science Experiment will use antennas to communicate with the Earth for a very accurate determination of the gravitational field. The signal from the Earth will be immediately relayed, and a shift in its frequency due to the Doppler effect will allow us to determine small changes in speed due to the unevenness of the gravitational field of Jupiter.

A directional antenna will be used in this experiment.

Magnetometer (MAG)taken out to the side at the end of one of the solar panels (this is a standard solution, everywhere magnetometers try to remove away from the working electronics of the device) will make it possible to draw a three-dimensional map of the magnetic field of Jupiter.

In the experiment "particle distribution in aurora" (JADE), three electronic sensors and one ion will capture particles of aurora.

A high-energy particle detector (JEDI) of three identical sensors will determine how high-energy particles flying in the vicinity interact with Jupiter’s magnetosphere. A large number of such particles fall into the trap of the magnetic field of Jupiter and burns with polar lights at the poles.

Infrared Aurora Cartographer (JIRAM)will allow you to get the spectra of auroras and find out the composition of the atmosphere around them.

An ultraviolet spectrograph (UVS) will make it possible to remotely find out the composition of the upper atmosphere in a different range by adding JIRAM.

The Waves instrument of two antennas will record radio and plasma waves in the vicinity of Jupiter. One antenna is not structurally very different from those that once stood as “horns” on televisions, and the second is an ordinary magnetic coil.

And finally, the JunoCam cameraIt does not carry a serious scientific load, but was added for the purposes of popularization and public relations. A camera operating in visible light will have to take at least 7 orbits to take beautiful photographs, and then it will fail in the radiation hell where Juno will dive every turn.

All instruments are installed on the sides of the device, and, in the "Juno" operating mode, they will either look into the depths of Jupiter, then "rest" and calibrate, looking in the opposite direction.

Waltz of Fallout

The rotation of Juno is a conscious decision. Of the many methods of orientation and stabilization of spacecraft, stabilization by rotation allows you to "maintain" the desired position on one axis "for free", spending fuel only on spinning up the device and does not require electronics to maintain a steady orientation. Under the conditions of powerful magnetic fields and high-energy particles, a full-fledged three-axis orientation may fail and put the device into protected mode with the loss of the scientific program at this turn, and the spinning top of the Juno will maintain its correct position in case of any failure of any electronics. On the way to Jupiter, "Juno" rotated at a speed of 1 rpm, the scientific operating mode is 2 rpm, and for maneuvers the device will spin up to 5 rpm.

The exclusion of electronics from controlling the probe in the most radiation-hazardous areas is not the only measure to combat Jupiter's electromagnetic anger. For the mission, the surface of the device will receive a dose of 11 megarads or 110 thousand sievert. For comparison - 1 sievert received at one time is the beginning of radiation sickness in humans, and a dose of 6 sievert is already deadly. Electronics is stronger than flesh, but such doses would be fatal for her too. Therefore, on Juno there is a radiation "shelter" of titanium 1 cm thick and a total mass of 200 kg. Inside it, electronics should receive only 25 kilorad (250 sievert) for the entire mission, while the electronics is designed for a twice as large dose. Electronics that cannot be placed in the bunker must be protected in place, for example, more than half of the mass of the star sensor is protected against radiation.

37 jumps to hell

The braking of Jupiter on July 4/5 will be the beginning of the mission. Having reduced its speed by 542 meters per second, the Juno will enter preliminary orbit for a period of 53.5 days. If braking is not successful, then the probe will forever warm up with Jupiter. Therefore, at this stage, just in case, all scientific devices will be turned off so that there is no random interference. After two orbits in the preliminary orbit, the Juno will enter the scientific orbit for a period of 14 days.

In this highly elliptical orbit, the Juno will periodically dive into close proximity to Jupiter (to an altitude of 4-8 thousand kilometers from the level of the clouds) and again depart beyond Callisto’s orbit. Due to the rotation of Jupiter, the orbit will pass over different meridians each time, and the device will be able to fly over the entire surface, which will create three-dimensional maps of the magnetosphere of all of Jupiter.

If everything goes according to plan, then at the 37th turn, Juno will perform the last maneuver and burn up in the atmosphere of Jupiter on February 20, 2018.

Poverty and Radiation Deficit

The total project cost is estimated at $ 1.1 billion in 2011. This is not much for space, therefore, among technical solutions you can find those that, depending on your mood, can be called a triumph of ingenuity or forced tricks from poverty.

First of all, the Juno did not fly straight to Jupiter. In order not to use a more load-bearing and more expensive launch vehicle, the probe was launched first into the orbit of Mars, and then conducted a gravitational maneuver near the Earth.

This decision allowed to increase the speed by 70%, but due to the need to return to Earth, “Juno” flew an extra two years. Considering that the development of the device began in 2006, it turns out that people will give this project 12 years of their life. In this case, scientists and engineers will be able to participate in only one, if very lucky, two space projects in their scientific career. And that is a little sad.

Secondly, large solar panels, very high-tech, which are praised so much now, are far from an ideal solution. In Jupiter’s orbit (5 AU), the Juno will receive only 1/25 of the Sun’s energy, compared with the Earth’s orbit. Therefore, a probe with open panels exceeds 20 meters in width, and the weight of the panels is 340 kg. At the same time, small, lightweight, working without a control systema radioisotope generator (RTG) would be a much better choice, providing Unon with heat and electricity. But in the USA, the production of their plutonium-238 for RTGs was stopped long ago, and, for example, Curiosity feeds and heats plutonium of Russian origin. In 2013, the production of American plutonium was resumed, but so far it is an expensive and scarce product.

PR burden

In addition to scientific tasks, Juno is also engaged in the popularization of science and astronautics, including for children. Firstly, the JunoCam camera was added for our pleasure - it will delight us with beautiful photographs of Jupiter for the first seven turns. They even say that the public will be able to participate in the selection of goals for photographing. Secondly, NASA entered into a partnership agreement with LEGO, and three Lego figures fly on the device: Jupiter, Juno and Galileo Galilei.

And at the press conference there was a “Juno” model from Lego.

We hope that this will inspire some of the future scientists, engineers or astronauts.

Epilogue

We don’t know what photos JunoCam will show us. But we know that, flying in the polar orbit, the Juno will look at Jupiter from above and below. To finish on a major note, I tried to find some spectacular angles of what we can see over the next months. And the wonderful SpaceEngine sandbox planetarium helped me with this.

Jupiter is always visible to us from the Earth completely lit. But the device in its orbit can take a photo of the crescent of the planet. And the shadow from one of the Galilean satellites will additionally decorate the picture.